GAMAMOD

GAMAMOD is an optimization model for the complete German Gas Grid during the period of an entire year with daily resolution. It contains more than 800 nodes and 1200 edges, while also taking into account parallel transmission lines, storage, and changes to demand and the grid as year progress. Its main outputs are optimal flow, imports, storage usage and retrofitting potential.

The Linear Program (LP) version of the model was developed in order to simulate the behaviour of the German Transmission Grid and assume optimal use of resources. The Mixed-Integer Linear Program (MILP) was developed in order to calculate optimal retrofitting, and while it uses a similar inputs, its objective is to calculate the maximum available pipelines for retrofitting assuming that the Transmission Grid is used in a way that prioritizes retrofitting over optimal transmission. 

Given the higher solving complexity of MILP an iterative heuristic was implemented to obtain solutions to this problem. In the first iteration, the discrete variable u_e is relaxed such that it is continuos in [0, 1]. Once this LP formulation of the problem is solved, the results are analysed and either fixed as 0 or given binary initial values. The reduced model is then solved as a MILP.